The invention relates to a method for processing hydrophilic polymer into an elastomer compound, hydrophilic polymer filled elastomers made by said method, and tires made using hydrophilic polymer filled elastomer.
Prior art composites used in the tire industry comprise rubber compositions, for example composites based on styrene butadiene rubber (SBR), polyisoprene rubber, polybutadiene rubber, polychloroprene rubber, nitrile butadiene rubber (NBR), ethylene propylene diene monomer rubber (EPDM), natural rubber and mixtures thereof. It is continually a goal in the tire art to provide rubber compounds that enhance traction properties while providing good rolling resistance properties and good wear properties.
Certain hydrophilic polymers may be derived from starch. As described by Novon Products, a Division of Warner-Lambert company, 182 Tabor Road, Morris Plains, N.J., starch consists of two types of glucose polymers, linear amylose and branched amylopectin. The distribution of these two polymers effects the properties of the starch. Although starch in dry form is not thermoplastic, it forms a melt in the presence of a plasticizer such as water. The large number of hydroxyl groups in the starch molecule import a hydrophilic character to the molecule that limits its applicability in the preparation of plastic substitutes based on native starch, but to increase the range of viable applications of starch based plastics in product use, native starches can be blended with degradable synthetics. As little as 1% by weight synthetic polymer greatly improves the stability of the starch based plastic substitutes. Since the goal of Novon is to improve the environment by producing biodegradable plastics, Novon notes that when other degradable polymers are blended with starch, or the starch is modified to improve properties or processability, the rate of biodegradation will change. For Novon, the challenge of developing starch-based plastic substitutes is to improve the properties while maintaining acceptable degradation rates, and quantification of biodegradation rates in wastewater, soil, and compost environments is an important part of the product development process.
Starch materials have been used as model systems in investigations of physical and engineering properties of foods. Isothermal absorption of water in starch gels give low water diffusivities which decrease at lower moisture contents (Fish 1958).
Destructured starch compositions that have dimensional stability and hydrophilic properties have been described by Warner-Lambert in EPA 409,789, EPA 409,788, EPA 404,728, EPA 404,727, EPA 404,723, U.S. Pat. No. 5,095,054, issued Mar. 10, 1992, and Plastics News Special Edition, Jun. 18, 1991 pages 2/29.
It is believed that similar compositions are produced by Archer-Daniels-Midland and Epron Industries, Ltd.
In accordance with the present invention, the inventors herein have theorized that the hydrophilic properties of the starch based polymers, when used as a filler in a tire tread rubber, will provide enhanced traction on wet pavement, because of the wettability of the polymer, while providing good rolling resistance properties on dry pavement.
Accordingly, it is an object of the present invention to provide a method by which the properties of a rubber composite can be optimized for a particular use by adjusting the amount of hydrophilic polymers, and conventional reinforcing fillers (such as carbon black, silica, etc.) in the composite.
Other objects of the invention will be apparent from the following description and claims.